User's Guide

ThingMagic M6e User Guide 61
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Appendix C: Environmental Considerations
ElectroStatic Discharge (ESD) Considerations
ESD Damage Overview
In M6e-based reader installations where readers have failed without known cause, ESD has been found to
be the most common cause. Failures due to ESD tend to be in the M6e Power Amplifier (PA) section. PA
failures typically manifest themselves at the software interface in the following ways:
• RF operations (read, write, etc.) respond with Assert - 7F01 - indicating a fatal error. This is typically due
to the module not being able to reach the target power level due to PA damage.
• RF operations (read, write, etc.) respond with No Antenna Connected/Detected even when a known
good antenna is attached.
• Unexpected Invalid Command errors, indicating command not supported, when that command had
worked previously. A command may become unsupported when the reader, during its self-protection
routines, has returned to the bootloader to prevent any further damage. This jump to boot loader caused
by power amp damage occurs at the start of any read tag commands.
Determining that ESD is the root cause of failures is difficult because it relies on negative result
experiments, i.e., it is the lack of failure after a configuration change, rather than a positive flag wave that
identifies it as ESD. Such flag waves are sometimes available at the unpackaged transistor level under high
power microscopy. The remoteness of microscopic examination from the installed field failures is indicative
of the high cost of using such analysis methods for investigating ESD issues. Most ESD issue resolutions
use the negative result experiments to determine success.
ESD discharges come with a range of values with vaying degrees. There will be a distribution of ESD
intensities in some installations of the bare M6e that have an ESD failure problem. There may be an issue
without knowledge of a limit in the statistics of those intensities. For the bare M6e equipped with the
mitigation methods described below, there may be an occasional ESD discharge that exceeds any given
mitigation, resulting in failure. Many installations will have some upper bound on the value of ESD events
given the geometry of that installation.
Several sequential steps are recommended for a) determining ESD is the likely cause of a given group of
failures, and b) enhancing the M6e’s environment to eliminate ESD failures. The steps vary depending on
the required M6e output power in any given application.
Identifying ESD as the Cause of Damaged Readers
The following are some suggested methods to determine if ESD has caused reader failures, i.e., ESD
diagnostics. Some of these suggestions have the negative result experiment issue.
Warning: The M6e antenna ports may be susceptible to damage from Electrostatic Discharge
(ESD). Equipment failure can result if the antenna or communication ports are
subjected to ESD. Standard ESD precautions should be taken during installation to
avoid static discharge when handling or making connections to the M6 reader
antenna or communication ports. Environmental analysis should also be performed
to ensure static is not building up on and around the antennas, possibly causing
discharges during operation.